i have a 99XJ and am having some weird venting issues. i did seach but couldnt find the answer i am looking for so im starting a new thread so maybe someone can help me. on to the problem...

first, when im going up hill and the engine has to work harder to stay at speed the a/c will switch from the dash vent and go to defrost and will stay there till i let off the gas.

second, if im on the interstate the a/c seems to wanna switch and acts like its stuck and blows behind the dash and will stay like that till i shut it off.

last, i have no heat. i know right now its not needed but i havbe a 6yr old and am expecting my new son anyday so i will need it before winter. when i put it on heat it seems to get room temp but nothing more.

today i took the dash apart and looked and everything i could get to and it all seem to work right. i looked under the hood but honestly i dont know much about vacuum setups so i looked for cracked and broken vacuum lines but didnt see anything, that doesnt mean there isnt but i may have over looked something.

thanks in advance

 

If it keeps changing at the different vents it is a vacuum leak. If you couldn't find a leaking hose you might want to check the vacuum ball behind the front bumper passenger side. Also go over all the hoses again. Sometime it can be hard to find a leak if it is real small. As for the heater. You heater core may be plugged. A quick way to check that is to let it get up to normal operating temp with the heater on high and feel the heater hoses. The both should be hot. If only one is, More then likely it's plugged.

 

ok im gonna check them again and feel the heater hoses also. thanks

 

Not a problem. Let us know what you find and if the problem prosiest we can go from there.
Good Luck!

 

ok i went out to the garage and checked the vacuum lines with wd40 ( read that on another thread) didnt notice anything but i could have missed a small leak. and ur method for checkin the heater core worked, inlet hose was really hot and lower hose was just warm.

 

Did you check the vacuum ball for cracks?

 

i gave it a quick look but had to get my son. will check it tomorrow

 

went to my buddys shop today to see if he could help me and we found the problem, it was the check valve off the intake manifold. on the way home everything seemed to work fine( fingers crossed) it stays like that.

part only cost $9.99 so im pretty happy about that. thanks for your help RTorrez1